Ascending Sensory & Descending Motor pathways

Question 1

Neuromuscular Spindle function, location, and type of fiber?

Answer 1

Muscle stretch and position sense (proprioception)
all striated muscles
A-alpha very fast conducting

Question 2

Meissner Corpuscle function, location, and type of fiber?

Answer 2

Discriminative touch
Concentrated in finger tips
A-beta fibers - fast conducting

Question 3

Pacinian Corpuscle function, location, and type of fiber?

Answer 3

Detection of vibration
Concentrated in fingers and palms
A-beta fibers - fast conducting

Question 4

Merkel Nerve Ending function, location, and type of fiber?

Answer 4

Discriminative touch
Concentrated in fingertips
A-beta fibers - fast conducting

Question 5

What do Free Nerve ending give the sensation of?

Answer 5

Pain
Crude touch
Temperature

Question 6

Fast pain

Answer 6

Carried by A-delta fibers
Arrives in CNS relatively quickly
Precise location of stimulus
Awareness of tissue damage

Question 7

Slow Pain

Answer 7

Carried by C fibers
Arrives in CNS relatively slowly
Poor location of stimulus
Nagging sensation of lingering pain

Question 8

Axon Reflex

Answer 8

1. Skin is scratched
2. Skin reddens due to capillary dilation
3. Free Nerve Ending discharge and conduct signal to the -> spinal cord (orthodromic conduction) -> Branches (antidromic conduction -> release of substance P, Arteriolar dilation - the flare, Activation of Mast Cells - release of histamine, Increased Capillary Permeability - the wheal

Question 9

Discriminative Touch Pathway (two-point discrimination)

Answer 9

Posterior Column System:
A-beta fiber -> collateral to lamina II -> decussates in medulla -> Relays in Thalamus (anterior posterolateral nucleus) -> Terminates in postcentral gyrus

Question 10

Fast Pain

Answer 10

A-Delta fiber -> Lamina I -> Decussates in cord -> Relays in Thalamus (VPL) -> Terminates in postcentral gyrus

Question 11

Slow Pain

Answer 11

C fiber -> Lamina II -> Excitatory interneuron -> Lamina V -> Brainstem Reticular formation -> Relays in Thalamus (intralaminar nuclei) -> Many regions of Cortex

Question 12

Define Lower Motor Neuron

Answer 12

Innervates striated muscle, last neuron in chain of neurons

Question 13

Lower Motor Neurons include:

Answer 13

Alpha motor neuron - extrafusal muscle fibers

Gamma motor neuron - intrafusal muscle fibers

Question 14

A lesion of the Lower Motor Neuron may cause:

Answer 14

Atonia - loss of muscle tone
Areflexia - loss of myotatic (knee jerk) reflex
Flaccid paralysis
Fasciculations - spontaneous muscle contractions
Atrophy - loss of muscle tissue

Question 15

Course of Corticospinal (Pyramidal) Tract

Answer 15

Origin 60-80% from motor cortex -> Internal capsule -> Cerebral Peduncle (midbrain) -> Pyramids (medula) >–(Decussates)–> Terminates in spinal cord gray matter

Question 16

Function of Corticospinal Tract

Answer 16

Facilitates: 
Extensor muscles in upperextremity
Flexor muscles in lower extremity
Primary effect:
Control of hand musculature

Question 17

Lesion of the Upper Motor Neuron

Answer 17

Spastic paralysis
Hypertonus:
     Flexors of arm
     Extensors of leg
Hyperreflexia
Negative plantar reflex (Babinski sign)
Atrophy of disuse

Question 18

Rubrospinal Tract

Answer 18

Control of proximal arm & leg musculature

Question 19

Reticulospinal Tract

Answer 19

Control of axial musculature - walking

Question 20

Vestibulospinal Tract

Answer 20

Control of axial musculature - balance

Question 21

Raphe Spinal Tract

Answer 21

Control of incoming pain signals

Question 22

Which sensory receptors are encapsulated?

Answer 22

Meissner’s Corpuscle and Pacinian Corpuscle

Think: Corpuscle

Question 23

Which sensory receptors are not encapsulated?

Answer 23

Merkels nerve ending and free nerve endings

Think: Nerve endings